Which combination of atmospheric conditions will reduce aircraft takeoff and climb performance?

High temperature, high relative humidity, and high density altitude significantly affect aircraft performance by reducing the density of air. When the temperature increases, the air becomes less dense, which diminishes thrust and lift produced by the aircraft's wings and propellers. Additionally, high humidity means that there is more water vapor in the air, which further reduces air density because water vapor is lighter than the nitrogen and oxygen that make up most of the atmosphere.

High density altitude occurs at locations where elevation is high, or when atmospheric conditions (like temperature and humidity) decrease air density. The combination of these factors means that the aircraft must operate in thinner air, leading to poorer aerodynamic performance. This results in longer takeoff distances and reduced climb rates, making it more challenging to achieve safe operating margins during takeoff and ascent.

In contrast, the other combinations either involve conditions that would enhance performance or maintain a situation that does not significantly affect aircraft capabilities. For instance, low temperature and low density altitude usually contribute to better performance.